Field of the Invention
The invention lies in the field of printing technology. More specifically, the invention pertains to a fold-off guide in a folder assembly of a signature and sheet processing machine.
Fold-off guides are used, in general, in machines that fold substantially flat material with a rotary motion. In the printing machine context, these include jaw folders, pinless folders, rotary blade folders, quarter folders, gripper folders, and the like.
Fold-off guides used in paper product folders aid the signature or sheet in direction changes or sudden accelerations and decelerations. Such accelerations and decelerations often lead to dog-ear formation and print smearing of the freshly processed paper. Conventional fold-off guides are fixed radius guides. While these are helpful to a certain extent, they cannot accommodate the varying needs during product fold-off subject to speed changes. Also, with the ever-increasing speeds, fixed radius fold-off guides have proved to be inadequate.
It is accordingly an object of the invention to provide a fold-off guide in a folder of a paper-processing machine, which overcomes the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and which allows better control through present speed range and allows further increases in the folder speed while reducing dog-ear formation and signature marking.
With the foregoing and other objects in view there is provided, in accordance with the invention, a folder in a signature-processing machine, comprising:
a transfer cylinder and a folding cylinder mounted to be rotatable in relative counter-rotation at a substantially equal peripheral speed, and disposed to form a nip having an entry side and an exit side defined by the rotation of the transfer cylinder and the folding cylinder;
the transfer cylinder being configured to transport a signature with a leading edge and a trailing edge; the folding cylinder having a device for taking up the signature at a folding location between the leading edge and the trailing edge, folding the signature at the folding location, and slaving a tail of the signature with the trailing edge and the leading edge away from the transfer cylinder and along with the folding cylinder; and
a fold-off guide disposed at the exit side of the nip, the fold-off guide having a fold-off surface movably disposed for changing a position of the fold-off surface during a given print job.
In accordance with an added feature of the invention, the fold-off guide is a flexible plate mounted in two clamps extending parallel to a transfer cylinder axis.
In accordance with an additional feature of the invention, one or both of the clamps is rotatably disposed about an axis parallel to the transfer cylinder axis for changing a shape of the flexible plate by bending the plate upon a rotation of the at least one of the clamps.
In accordance with another feature of the invention, the fold-off guide is an endless belt mounted to circulate about a plurality of guide rollers and forming a dynamically movable fold-off surface moving in a vicinity of the folding cylinder at a substantially equal speed with a periphery of the folding cylinder.
In accordance with a further feature of the invention, the folding cylinder is a jaw cylinder carrying at least one jaw configured to fold the signature.
In accordance with yet a further feature of the invention, the transfer cylinder is a pin cylinder or a gripper cylinder carrying at least one tucking blade for tucking the signature at the folding location into the jaw of the jaw cylinder.
In accordance with a concomitant feature of the invention, the fold-off guide is a cam cylinder formed with at least one lobe and rotating in synchronicity with the signatures being transported through said nip.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a fold-off guide in a folder of a sheet processing machine, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.